身體跨在東西兩側
這一家就是核心畫面本身，還沒有任何引申。跨的是真的腿，被跨的是真的東西。
verb · B2
To sit or stand with one leg on each side of something, so that the thing is between your legs.
跨坐；跨站
核心畫面
One body, two sides. Picture a line painted on the ground and a person standing over it with one foot on each side. They are not on this side, and not on that side; they are on both at the same time. Every use of straddle can be read as that same picture getting larger. The line becomes a river, then a national border, then the edge between two subjects, then the two halves of an argument. Whatever is in the middle stays in the middle, and whatever straddles it keeps touching both sides at once.
可以想成這樣一個畫面：地上畫了一條線，一個人站在線上，一腳踩這邊，一腳踩那邊。他不算在這邊，也不算在那邊，他同時在兩…更多收起
可以想成這樣一個畫面：地上畫了一條線，一個人站在線上，一腳踩這邊，一腳踩那邊。他不算在這邊，也不算在那邊，他同時在兩邊。straddle 的各種用法，就像這個畫面被一路放大：中間那條線先變成一條河，再變成一道國界，然後變成兩個學科之間的分界，最後變成一場爭論的正反兩方。被跨住的東西一直留在中間，而跨住它的人或東西，兩邊都碰得到。From the word’s history
The source says the verb is recorded from the 1560s and is most likely an altered form of the dialect word striddle. That is as far as this evidence goes; no older root is given, so treat it as a note about the word's age rather than an explanation of the picture.
資料說這個動詞從 1560 年代就有紀錄，來源「很可能」是方言字 striddle。線索到這裡就停了，沒有更早的字根，所以把它當成一個年代的註記就好，不要當成上面那個畫面的來源解釋。
Wiktionary entry for straddle (source_ref kaikki:3f6f69a190036ae4:1199473810): "As a verb, attested since the 1560s. Most likely, an alteration of dialectal striddle."
Three branches
地形與建築橫跨一條界線
把跨的人換成一座山、一個村子或一棟房子，把中間那樣東西換成一條河或一道界線，姿勢完全一樣，只是尺寸變大了。
verb · B2
If something such as a mountain, a town, or a building straddles a line, a road, or a river, part of it is on one side of it and part of it is on the other side.
橫跨；橫亙在…兩邊
同時屬於兩邊
中間那條線變成看不見的：兩個領域之間、兩種語言之間、兩段時間之間，甚至一場爭論的兩方。腳還是一邊一隻。
verb · C1
To belong to, cover, or join two or more different areas of activity, groups of people, or periods of time at once, instead of fitting inside only one of them.
橫跨（兩個領域、兩群人或兩段時間）